1. Field Of The Invention
The present invention relates generally to a flow volume calibrator for a spirometer and, more specifically, to a flow volume calibrator which provides accurate calibration of spirometers by controlling the temperature and moisture content of gas which it receives and accurately measuring the flow rates of gas it receives and discharges.
2. Description Of The Prior Art
In recent years, machinery for evaluating lung function, e.g., spirometers, has experienced commercial success and has found wide acceptance and application. Generally, this machinery measures the forceful exhalation or inhalation of a patient's breath, i.e., the volume of air inhaled or exhaled by a patient over a certain time period. It must consistently perform these measurements with a high degree of accuracy.
To insure the accuracy of spirometers and similar apparatus, those working in the art have proposed a number of calibration devices which produce an exhalation or inhalation action having predetermined characteristics which a user may compare to the output of the spirometer. Desirably, these devices should provide gas having the same temperature and moisture level as the breath of a patient. In addition, they should provide flow rates for a wide variety of volumes.
One known device is a large syringe that provides a predetermined volume of air for calibrating a spirometer. To measure the time which it takes to force the volume of air contained by the syringe into the spirometer, the user must coordinate the movement of the syringe's plunger with a timer. Since many acceptable standards require testing at time intervals of a second or less, a user cannot obtain accurate time and volume readings. In addition, this prior calibrator does not adjust the temperature and moisture content of the gas it receives.
The calibrator of the present invention fulfills the requirements outlined above and avoids the shortcomings of the prior calibrators. It is a simple construction which can adjust the temperature and moisture content of the gas it receives and which provides flow rates for a wide variety of volumes.